This invention relates to a method for automatically changing bobbins and winding yarns continuously threrupon and an apparatus for working this method. More particularly, the invention relates to a revolving-type winding method in which a yarn is continuously wound on bobbins held on bobbin holders rotatably mounted on a rotatable turret while automatically replacing a fully wound bobbin with an empty bobbin, and to an apparatus for practising this winding method.
In conventional continuous yarn winding apparatuses including an automatic bobbin exchange mechanism, for example, as is disclosed in the specification of British Pat. No. 1,332,182, a yarn to be transferred from a full bobbin to an empty bobbin is caught by yarn-guiding fittings fixed to the end of a bobbin holder for holding a bobbin thereon, or by thread-guiding fittings held on a bobbin holder with a bobbin.
When the bobbin exchange is conducted by using such conventional apparatus, a yarn wraps around the yarn-guiding fittings in a complicated manner and such operations as the treatment of the yarn end after doffing of a full bobbin and the dismounting and mounting of yarn-guiding fittings become complicated. Accordingly, various difficulties are involved in automating treatments subsequent to the doffing step and, if these treatments are made automatic, equipment costs are tremendously high so that no economical advantages can be attained.
For overcoming these difficulties, it was proposed to form a yarn-catching circular groove on a bobbin. However, when bobbins having a groove on the periphery thereof are employed, the ratio of success in catching the yarn end is very low, resulting in reduction of productivity and operational efficiency. Especially when it is intended to perform the bobbin exchange automatically, this defect becomes a serious obstacle.
As a result of our investigations made to clarify why the ratio of success in catching the yarn end is low in the method using bobbins having a circular groove formed on the periphery thereof, we found that since the yarn is maintained under excessive tension when it is about to be engaged with the circular groove of a bobbin, it is very difficult for the bobbin to hold the yarn by the circular groove, and that since the yarn is not properly aligned with the circular groove, the yarn cannot be engaged with said circular groove.
A yarn-guide or the like may be used for aligning a yarn with a circular groove, in order to avoid said problem. However, if a yarn-guide or the like is used, the yarn is relaxed in the vicinity of the bobbin. Since a yarn in the relaxed state has a property that it is likely to wrap around a rotary member disposed in the vicinity thereof, for example, a roller or the like, winding of the relaxed yarn on a roller located in the vicinity of the yarn passage is enhanced as well as winding of the yarn on the bobbin. Further, properly alignment of the yarn with the circular groove on a bobbin cannot be obtained even if the utmost efforts are made using the conventional method, because limitations are imposed on the precision of positioning the groove and the yarn is inevitably unstable when travelling.
It is a primary object of this invention to provide a method and apparatus for automatically changing bobbins and winding yarn continuously thereupon, in which the above-mentioned defects and disadvantages involved in conventional techniques can be overcome, namely such method and apparatus in which full bobbins, where the yarn ends can easily be handled as steps subsequent to doffing, can be obtained and exchange of bobbins can be done very smoothly without troubles.
In the method of this invention for automatically changing bobbins and winding yarn continuously thereupon, a yarn catching groove is formed at the end of a bobbin instead of yarn-guiding fittings used for catching the yarn in the conventional techniques. On exchange of bobbins a turret is rotated in a direction opposite to the rotational direction of the bobbins, so that the yarn is aligned with the groove and engaged with the grooved bobbin.
An apparatus of this invention for automatically changing bobbins and winding yarn continuously thereupon, which is used for practising the aforesaid method smoothly and assuredly, comprises a turnable turret on which a plurality of bobbin holders for holding bobbins are rotatably mounted, means for rotating the bobbins held on said bobbin holders, and traverse means for traversing said yarn upstream of said bobbin holders in the axial direction thereof, means for turning said turret to alternate exchange positions of bobbins held on said bobbin holders between a winding position and a standby position, an improvement comprising in combination, said turret turning means being capable of turning said turret in a direction opposite to the rotational direction of said bobbins, a guide disposed upstream of said yarn traverse means for disengaging said yarn from said yarn traverse means, and a yarn catching groove formed at a peripheral portion of each bobbin.